Urethral behavior during the involuntary detrusor contraction.

The bladder-urethral pressure records of 77 patients with involuntary detrusor contractions have been reviewed to described the behavior of the urethra in relation to the involuntary detrusor contraction. The involuntary detrusor contraction is preceded by a fall of urethral pressure in a manner similar to that observed with normal voiding. Parasympathetic blockade will completely or partially prevent the detrusor contraction with a limited effect upon the urethral pressure fall. The meschanism proposed is an interruption of synpathetic effect in the urethra and bladder with parasympathetic stimulation of the detrusor as in normal voiding. The stimulus of this mechanism in the involuntary detrusor contraction is not known; however, a wide range of possibilities should be considered.